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The present invention pertains generally to space launch vehicles. More particularly, the present invention pertains to a configurable space launch system of space launch vehicles. The present invention is particularly, but not exclusively, useful for providing assembly of components of a space launch vehicle selected to accomplish a specific mission or task at the lowest possible cost.
Manned and unmanned spacecraft have ventured far beyond Earth and its sensible atmosphere. Space exploration activity has collected valuable data about human and other biological, physiological and psychological reactions to the space environment. Other space exploration activities have greatly expanded our knowledge of Earth, its moon, the solar system and the universe.
Parallel with space exploration activity, substantial use of Earth orbits for military and commercial applications have developed. Presently, the majority of space launches are for military and commercial purposes. Examples include communications satellites, weather satellites, Earth observation satellites, and navigation satellites.
The feasibility and capability to launch spacecraft into Earth orbit, and beyond, clearly has been demonstrated. The size of a space launch vehicle is primarily a function of the payload mass, the apogee of the operational orbit, the perigee of the operational orbit, the inclination of the operational orbit, and the technology applied in the launch vehicle design. The cost of a space launch typically is tens to hundreds of million dollars. Reducing costs, therefore, associated with multiple and frequent space launches is a primary goal of space activity.
Reusability of space launch system components is a logical and presently favored path to lowering the costs associated with a space launch. The U.S. National Aeronautics and Space Administration Space Shuttle is a partially reusable system. The solid rocket booster units associated with the Space Shuttle are recoverable; after a parachute landing of a booster unit in the ocean, parts of a booster may be recycled. The orbiter unit associated with the Space Shuttle has thermal protection, an aerodynamic shape adequate for providing lift in a variety of situations, aerodynamic control surfaces, the capability of entering Earth orbit and returning to Earth""s surface for horizontal landing on a runway, and therefore is recoverable intact for later launches. The orbiter unit was the first operational xe2x80x9cspaceplane.xe2x80x9d The third system component of the Space Shuttle is a single external tank, which is expended after each launch. The basic design of the Space Shuttle was done in the 1970""s.
At least one principal disadvantage of the manned Space Shuttle is the relatively high cost per flight, which, in fact, is higher than contemporary unmanned expendable launch vehicles of the Atlas, Delta, Ariane and Proton families. Therefore, what has been sought in the industry, but not achieved, is a new configuration with a cost-per-flight lower than contemporary expendable launch vehicles.
Considerable study, analysis and preliminary design activity has focused on a fully reusable single spaceplane. Unfortunately such an approach, while theoretically possible, has been found to be impractical in terms of technological risk. A relatively small increase in the dry weight of the single spaceplace results in an unacceptably large increase in the gross lift-off weight of the vehicle. Further, projected development costs are quite high. Another approach involves two fully reusable spaceplanes of different sizes, one spaceplane being a large reusable booster, and a smaller reusable spaceplane attached to the first in parallel. This approach reduces some of the technological risk associated with a fully reusable single spaceplane, but because two separate reusable spaceplanes must be developed, development costs appear prohibitive.
Over the past decade, numerous alternative efforts have examined various vehicle configurations for lowering the cost-per-flight. The typical result is a concept that requires considerable expense to develop, acquire and operate, that can be applied only to relatively low mass payloads, or both. Therefore, there is a continuing need in the industry for a new, useful and improved space launch system of vehicles that is capable of providing the lowest cost-per-launch possible for a broad spectrum of space launch missions.
The principal components of cost-per-flight are launch site operations, launch range operations, propellant, expendable hardware, turn-around costs for reusable hardware and financial return. At least one way to assess required financial return per flight is the technique of Internal Rate of Return. For example, the development and initial fleet purchase cannot exceed $1.5B if (a) the development period is four years, (b) the operations period is six years, (c) the launch rate is 25 per year, (d) the required Internal Rate of Return is 30%, and (e) the cost per flight is to be fifty percent of contemporary expendable vehicles. That, in turn, emphasizes the need for relatively low development investment and relatively low investment in the initial fleet of reusable hardware.
The present invention responds to the significant challenges in lowering the cost-per-flight of space launchings.
Although there are many challenges associated with low cost-per-flight space launches, the goal remains achievable. It would be desirable, and of considerable advantage, to provide a space launch system of vehicles that have the lowest cost-per-flight for a broad spectrum of space launch missions. To meet the need for low cost-per-flight, such a system of vehicles should have substantial commonality of components and technology. Each system family member, therefore, would have strong configuration similarities to all other family members. Throughout the decision process of selecting appropriate components for such a space launch system, the investment cost for system development and for initial fleet purchase of reusable components, if any, would be included in predicting cost-per-flight. Applying this overarching rationale, the lowest cost-per-flight is achieved by the present invention, a configurable space launch system.
Briefly, a configurable space launch system, according to the present invention, is a family of distinct vehicle configurations, wherein each configuration includes one or more system-common reusable spaceplanes and a plurality of detachably mounted liquid propellant tanks that are external to the one or more spaceplanes. In extending beyond the existing art, (a) each vehicle configuration excludes ascent propellant tanks permanently installed inside, or integrated into, a reusable spaceplane, and (b) each vehicle configuration is operated in flight such that the number of in-flight staging points, where essentially empty external tanks and/or reusable spaceplanes no longer needed for acceleration thrusting are detached from the vehicle, is greater than the number of reusable spaceplanes in the configuration. The system-common reusable spaceplane has a payload bay dimensioned for the largest projected payload, incorporates one or more main rocket engines, and is capable of entering the Earth""s atmosphere for landing. Different vehicle configurations within the space launch system of vehicles will involve variations in the combination of number of spaceplanes; the number, size, and location of external tanks; and the number of in-flight staging points. The resulting space launch system is configurable because a vehicle configuration may be tailored for specific missions at optimal low cost-per-flight.
As used in this document, a xe2x80x9cspace launch vehiclexe2x80x9d travels from the surface of the Earth to Earth orbit and is comprised of one or more common spaceplanes and multiple external tanks.
A xe2x80x9cspaceplanexe2x80x9d is a component of the space launch vehicle, and is, at least, fully reusable by returning from orbit and landing intact, has an aerodynamic shape appropriate for atmospheric entry and flight and landing, can maneuver in space, has an aft compartment for main rocket propulsion, contains sensors and electronics for navigation and guidance, and has a bay for mission specific payloads and equipment.
An xe2x80x9cexternal tankxe2x80x9d contains ascent liquid propellant that is expended during flight to Earth orbit, and is detachably mounted external to the spaceplane or spaceplanes.
An xe2x80x9cin-flight staging pointxe2x80x9d is an event in a vehicle""s flight where essentially empty external tanks, or spaceplanes no longer needed to provide thrust, are released from the space launch vehicle.
A xe2x80x9cvehicle configurationxe2x80x9d is the specific sizing, assembly arrangement, and cooperative attachments of the one or more spaceplanes and the external tanks.
xe2x80x9cConfigurabilityxe2x80x9d and xe2x80x9cconfigurexe2x80x9d and xe2x80x9cconfiguredxe2x80x9d mean the capability to judiciously select a number of common spaceplanes, a number of variously sized external tanks and a number of in-flight staging points such that the resulting vehicle configuration will have optimal low cost-per-flight for a specific launch mission.
A xe2x80x9cconfigurable space launch systemxe2x80x9d is a set of vehicle configurations that use common spaceplanes and cost effective external tanks to provide a broad range of payload mass, payload volume, and destination orbits for low cost transportation to Earth orbit.
A vehicle""s xe2x80x9cconfiguration governing prescriptsxe2x80x9d is a unique set of prescripts governing all vehicle configurations comprising a configurable space launch system. The present invention reduces cost per flight by assembling a configurable space launch system of vehicles that satisfies the configuration prescripts, which include:
1. All vehicles incorporate one or more common reusable spaceplanes and multiple external ascent propellant tanks (collectively, xe2x80x9cvehicle componentsxe2x80x9d). Ascent propellant is the energy source for lift-off and acceleration to orbital velocity. This provides high vehicle efficiency (ratio of payload weight to vehicle gross lift-off weight) because of staging advantages and provides higher vehicle mass fractions (propellant weight to vehicle gross weight).
2. 90-100 percent of total ascent propellant volume is located in the external tanks. 0-10 volume percent may be in easily removable auxiliary tanks in a spaceplane payload bay, if space is available. Analyses by the inventors have demonstrated that placing propellant inside a spaceplane decreases vehicle performance and increases vehicle cost-per-flight. The performance decrease stems from the much larger volume of a spaceplane that contains large volumes of propellant; that volume increase requires more structure, thermal protection, landing gear and control surfaces, all leading to a spaceplane weight increase that is considerably greater than the dry weight of external tanks. The cost increase of placing large amounts of propellant inside a spaceplane results in higher development cost, higher production cost and higher turnaround (between flights) cost for a larger spaceplane. By placing ascent propellant in external tanks, vehicle performance, depending on other configurability objectives, may be increased through additional vehicle in-flight staging points where essentially empty tanks are released.
3. The number of in-flight staging points in the flight trajectory is greater than the number of spaceplanes in the vehicle configuration. Sequencing an empty-then-drop scheme for external tanks provides additional staging. For example, a vehicle using two reusable spaceplanes may have three or more xe2x80x9cstagesxe2x80x9d of powered flight. Staging is well-established practice in missiles and space launch vehicles to improve efficiency because less vehicle gross weight means lower cost. Further, staging significantly reduces the performance and cost penalties of increases in dry weight of reusable spaceplanes. A person practicing the present invention, therefore, has more latitude to use proven technology with an attendant reduction in risk; lower development risk generally results in lower development costs. This prescript leaves open the option to use already space-qualified subsystems, further decreasing development costs and risks. An example is to use the existing Space Shuttle Main Engine in the spaceplanes of the present invention.
4. All vehicle configurations in the configurable space launch system of vehicles use a common spaceplane. This reduces spaceplane development costs. As additional vehicle configurations for different missions are selected, the spaceplane will be considered a space-qualified component.
5. All vehicle configurations in the configurable space launch system use cost effective external tanks. This lowers development costs and allows economies of scale (for example, a single factory for all shapes and sizes of tanks).
6. No permanently mounted or integrated ascent propellant tanks are installed inside a spaceplane. Internal tanks increase volume and complexity of the spaceplane and create more surface area that must have thermal protection. Such tanks increase weight that the spaceplane structure must carry, leading to increased cost of spaceplane development and production.
7. The spaceplane has a bay sized no larger than the major dimensions of the maximum sized mission-specific cargo anticipated to be carried to orbit. This minimizes size of a spaceplane, and decreases spaceplane development and production cost.
8. Different vehicle configurations within the configurable space launch system have variations in the combination of the number of spaceplanes, the number and size and location of external tanks, and the number and sequencing of the in-flight staging points. This is a principal objective of configurability. At relatively low cost, a new system family member may be added to provide low cost launches for a new set of mission requirements.
Unlike what is known in the present art, the present invention incorporates all eight prescripts in all vehicle configurations in a configurable space launch system.
In accordance with the present invention, therefore, a low cost-per-flight configurable space launch system becomes a family of launch vehicles of varying configurations using a common spaceplane and cost effective external tank tanks. The various launch vehicles provide a launch capability for a broad range of user requirements for payload mass and destination orbit.
All the vehicles in the family have one or more common reusable spaceplanes and multiple detachably mounted external ascent propellant tanks. The one or more spaceplanes and the multiple external tanks are mechanically connected to maintain structural rigidity. The mechanical connections incorporate quick-release mechanisms to allow disengagement during flight. The release mechanisms may be pyrotechnic, electro-mechanical, or other appropriate mechanism.
A spaceplane is reusable in part because, after a mission in space, a spaceplane may be returned to Earth and used again on another mission. A spaceplane is not considered an expendable system component of the configurable space launch vehicles of the present invention. A spaceplane also includes at least one rocket engine. At least one purpose for the engine or engines on a spaceplane is to provide thrust for lift-off from a substantially vertical orientation and acceleration to orbital velocities. A spaceplane engine also may assist in decelerating the spaceplane for de-orbit, and in maneuvering the spaceplane while in orbit. Each engine on a configurable space launch vehicle, according to the present invention, may be removed from a spaceplane, or may be installed or reinstalled in a spaceplane, thus enhancing the configurability of the space launch vehicle. In addition, each engine on a spaceplane may be repositioned on a spaceplane having multiple substantially identical engines.
The shape of a spaceplane is not pertinent to the present invention. A spaceplane, according to the present invention, as a vehicle component of a space launch vehicle, includes an aerodynamic shape adequate for providing lift in a variety of situations, has control surfaces, has the capability of entering space and returning to Earth""s surface, is recoverable intact, and is reusable in additional space launch missions with minimum post-mission maintenance and repair. Any number of spaceplane shapes, therefore, is possible. A spaceplane may include a body with at least one wing. A spaceplane with at least one wing may be maneuvered to land on Earth horizontally. As a nonexclusive alternative, a spaceplane may be a lifting body, one example of which may be substantially triangular shape from a top view. Such a version of a spaceplane may also include surface controls such as protruding stability control apparatus that also may give the spaceplane the ability to land on Earth horizontally. Alternatively, a spaceplane may have a substantially conical shape having surface controls permitting a spaceplane to land on earth in a substantially vertical orientation. As a vehicle component of a space launch vehicle, a spaceplane, therefore, according to the present invention, may have any aerodynamic shape.
A spaceplane, according to the present invention, includes a payload bay. A payload bay may be sized consistent with the major dimensions of the maximum sized cargo anticipated to be carried to orbit. A payload bay shall have the capability to contain deliverable cargo, returnable cargo, on-orbit mission equipment, a crew module, a passenger module, a propulsion kit for atmospheric cruise thrusting of a non-orbiting spaceplane that has been released at an early in-flight staging point, easily removable auxiliary ascent propellant tank or tanks, or special mission-specific spaceplane equipment or combinations thereof. Part of the outside surface of the crew and passenger module may be the outside surface of the spaceplane; all or part of the payload bay doors would be removed to accommodate the modules.
Unlike what is known in the art, the present invention does not use a propulsion kit for ferrying a spaceplane from a distant downrange runway back to the vicinity of the space launch site. In the present invention, a propulsion kit is used only for atmospheric cruise thrusting to extend the range of a non-orbiting spaceplane that has been released at an early in-flight staging point and is returning directly to the vicinity of the launch site. Therefore, a propulsion kit of the present invention does not require relatively high thrust air-breathing jet engines for takeoffs and climb to altitude.
To minimize size and reduce costs of the spaceplanes, unlike what is provided in the present art, no ascent propellant tanks are permanently installed in or integrated into the spaceplane basic structure or the spaceplane bay. A smaller spaceplane will require less structure, less thermal protection for atmospheric entry, and less power for control surface actuation, all contributing to less spaceplane cost and greater vehicle efficiency (the ratio of payload/cargo to the vehicle gross weight at liftoff). A smaller vehicle is a less costly vehicle.
A configurable space launch vehicle according to the present invention will also include multiple external propellant tanks. An external propellant tank may be a recoverable or expendable vehicle component. An external propellant tank, according to the present invention, may be used for fuel, for oxidizer, or for a combination of fuel or oxidizer. After the mission-specific combination of fuel and oxidizer in an external propellant tank are used, an external propellant tank may be jettisoned from the space launch vehicle. Jettisoning tanks is an in-flight staging point. The mass to be carried from the staging point onward is significantly reduced. Staging improves vehicle efficiency, and, hence, lowers costs. An external propellant tank may be mounted on and detached from a spaceplane, may be mounted on and detached from one or more other external tanks, may be mounted on and detached from one or more other spaceplanes, and may be mounted on and detached from any vehicle or system component of the present invention to provide the configurability needed for a specific mission or task. Configurability of the present invention includes the capability of mounting an external propellant tank on, or detaching it from, an upper surface of a wing of a spaceplane. An external propellant tank also may be mounted on and detached from a lower surface of a wing of a spaceplane. In yet another configuration, an external propellant tank may be mounted on and detached from a surface of the body of a spaceplane, regardless of the shape of a spaceplane, and regardless of whether a particular spaceplane is equipped with a wing. The capability to configure a space launch vehicle, according to the present invention, permits a wide variety and a number of variations in the assembly and positioning of external tanks and aft mounted engines on a spaceplane. A nonexclusive example of the configurability of the present invention is the ability to mount external propellant tanks on a spaceplane, on a surface of a wing of a spaceplane, and on the belly surface of a fuselage of a spaceplane. Likewise, an external tank may be mounted on any surface of a spaceplane not equipped with a wing.
A nonexclusive sample configuration of a configurable space launch vehicle according to the present invention includes what may be described as a xe2x80x9ctwinxe2x80x9d configuration. A configurable space launch vehicle having a twin configuration may include a first common reusable spaceplane. The first common reusable spaceplane includes at least one engine. The twin configuration also includes a second common reusable spaceplane. The second common reusable spaceplane also has at least one engine. A second common reusable spaceplane is capable of being connected to, and decoupled from, a first reusable spaceplane and an external tank or tanks. A twin configuration of the present invention, consisting in part of a first common reusable spaceplane and a second common reusable spaceplane, may be launched from a substantially vertical position. In a twin configuration of the present invention, the first reusable spaceplane and the second reusable spaceplane will include a payload bay.
In the twin configuration, the engine or engines in the first common reusable spaceplane and the second common reusable spaceplane may be installed in or removed from each spaceplane. Likewise, a configurable space launch vehicle, according to the twin configuration of the present invention, includes a first and second common spaceplane in which each engine on the first spaceplane and second spaceplane may be repositioned on each of the spaceplanes.
In a twin configuration of the present invention, one or more external propellant tanks may be mounted on and detached from the first spaceplane or mounted on and detached from one or more other external propellant tanks. Likewise, one or more external propellant tanks may be mounted on and detached from the second common spaceplane or mounted on and detached from one more other external propellant tanks. For example, one or more external propellant tanks may be mounted to and detached from the upper surface of a wing of the first common reusable spaceplane. One or more external propellant tanks also may be mounted to and detached from the upper surface of a wing of the second common reusable spaceplane. In addition, or alternatively, given the configurability of the present invention, one or more external propellant tanks may be mounted to and detached from the lower surface of a wing of the first common reusable spaceplane. Alternatively, or in addition, one or more external propellant tanks may be mounted on and detached from the lower surface of a wing of the second common reusable spaceplane. Alternatively, or in addition, one or more external propellant tanks may be mounted on and detached from the body of the first common reusable spaceplane as well as the body of the second common reusable spaceplane. The capability to configure a space launch vehicle, according to the present invention, permits a wide variety and a number of variations in the assembly of external tanks in connection with the configurable space launch vehicle. At least one nonexclusive example of the configurability of the present invention is the ability to mount external propellant tanks underneath the spaceplane, on a lower surface of a wing or wings of a spaceplane and on the belly surface of the body of a spaceplane. The configuration of two common reusable spaceplanes in combination with multiple separable external propellant tanks provides several advantages. Comparatively smaller spaceplanes may be used in a twin configuration because most or all of the propellant is external to the spaceplane. External propellant tanks enhance performance characteristics of the configurable space launch vehicle, and contribute to reduction in size of the common spaceplane.
The flight trajectory of the twin configuration may involve three in-flight staging points. For example, after lift-off the propellant mass consumed in both spaceplanes"" engines decreases the instantaneous gross mass of the vehicle. When the thrust of the second common spaceplane is sufficient for continued acceleration, the first common spaceplane and any essentially empty external tanks may be jettisoned; that is the first in-flight staging point. The jettisoned spaceplane may aerodynamically maneuver into a flight path to return to a landing runway, possibly near the launch site. The spaceplane, when descending to an appropriate cruise altitude, may be assisted by air-breathing jet engines mounted on the spaceplane bay doors or deployed from inside the spaceplane bay. Unlike what is known in the art, the present invention does not rely on deployable wings, fins, rotors, or propellers. These relatively low thrust engines will be for the purpose of maintaining cruise altitude and extending the range of the return flight. The jettisoned external tanks will follow a free fall ballistic trajectory until impacting the Earth""s surface, either on water or ground. Alternatively, the external tanks may deploy parachutes to provide a softer impact and allow recovery and reuse. The second spaceplane and remaining external tanks will perform a second powered flight acceleration segment. At an appropriate point, essentially empty external tanks are jettisoned; this is the second in-flight staging point. The external tanks follow a ballistic path to the Earth""s surface. The second spaceplane, which contains mission payload, and the remaining external tanks, perform the third powered flight acceleration segment into the mission orbit. The now essentially empty external tanks are jettisoned and de-orbited, or may be jettisoned on the second spaceplane""s return flight; this is the third in-flight staging point. In a manner similar to that just described, multiple in-flight staging points may be sequenced for other vehicle configurations. Unlike what is known in the art, the present invention requires, as part of the configuration governing prescripts, that the performance advantage of staging be incorporated beyond the classic concept of xe2x80x9cboostersxe2x80x9d separating from xe2x80x9cupper stagesxe2x80x9d.
Configurability of the space launch system permits operators to select a vehicle configuration that is most cost effective for a particular mission""s requirements for payload mass and mission orbital parameters. Using calculations, formulae, algorithms, software and hardware well known in the art, the operator determines the lowest cost-per-flight vehicle by examining various combinations of number of common reusable spaceplanes, number and size of external tanks, the arrangement, positioning and attachment assembly of the spaceplanes and external tanks, and the number and sequencing of in-flight staging points.
In light of the above, an advantage of the present invention is a configurable space launch system having a wide spectrum of mission capabilities through selection of the lowest cost-per-flight vehicle configuration within the configurable space launch system of vehicle configurations for individual mission requirement. This advantage is illustrated in FIG. 5 that shows an example of a configurable space launch system having five vehicle configurations.
The use of a common spaceplane for all vehicle configurations provides several advantages. Because only one spaceplane is developed or selected, development cost is lowered. The one common spaceplane has no permanently mounted or integrated internal ascent propellant tanks and has a payload bay just large enough for the maximum sized payload; the spaceplane size is minimized and development and production costs are lowered. Operational costs are lowered not only because of commonality, but also because after the return of any reusable spaceplane, the spaceplane will be inspected, maintained as needed, and the payload bay will be outfitted for any specific next mission.
Another advantage of the present invention is a configurable space launch system that may be used for manned or unmanned space activity using a variety of common vehicle components to minimize development costs and time, to minimize learning curves because technology for vehicle components already is known to users in the industry, and to permit earlier low cost operational capability.
Another advantage of the present invention is a configurable space launch system having a significant variable range of thrust to satisfy requirements of different and differing missions to be achieved in space.
Another advantage of the present invention is a configurable space launch system with vehicle components that may be selected from a wide array of known, proven, and inexpensive technology so as to reduce the costs of a given mission or task while using technology that has been proven to be effective.
Yet another advantage of the present invention is a configurable space launch system for which expendable hardware may be designed using less expensive materials.
Another advantage of the present invention is a configurable space launch system, and a method for configuring such a system, which respectively are easy to use and to practice, and which are cost effective for their intended purposes.
These and other objects, features, and advantages of such a configurable space launch system that will become apparent to those skilled in the art when read in conjunction with the accompanying detailed description, drawing figures, and appended claims.
The foregoing has outlined broadly the more important features of the invention to better understand the detailed description, which follows, and to better understand the contribution of the present invention to the art. Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in application to the details of construction, and to the arrangements of the components, provided in the following description or drawing figures. The invention is capable of other embodiments, and of being practiced and carried out in various ways. Also, the phraseology and terminology employed in this disclosure are for purpose of descriptions and should not be regarded as limiting.
As those skilled in the art will appreciate, the conception on which this disclosure is based may be readily used as a basis for designing other structures, cooperation of structure, methods, and systems for carrying out the purposes of the present invention. The claims, therefore, include such equivalent constructions to the extent that equivalent constructions do not depart from the spirit and scope of the present invention.
The abstract associated with this disclosure is neither intended to define invention, which is measured by the claims, nor intended to be limiting as to the scope of the invention in any way.